/*
 * Copyright (c) Kumo Inc. and affiliates.
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#pragma once

#include <string>
#include <vector>

#include <melon/expected.h>
#include <melon/range.h>

namespace melon {
    /*
     * json_pointer
     *
     * As described in RFC 6901 "JSON Pointer".
     *
     * Implements parsing. Traversal using the pointer over data structures must be
     * implemented separately.
     */
    class json_pointer {
    public:
        enum class parse_error {
            invalid_first_character,
            invalid_escape_sequence,
        };

        class parse_exception : public std::runtime_error {
            using std::runtime_error::runtime_error;
        };

        json_pointer() = default;

        ~json_pointer() = default;

        /*
         * Parse string into vector of unescaped tokens.
         * Non-throwing and throwing versions.
         */
        static Expected<json_pointer, parse_error> try_parse(StringPiece const str);

        static json_pointer parse(StringPiece const str);

        /*
         * Return true if this pointer is proper to prefix to another pointer
         */
        bool is_prefix_of(json_pointer const &other) const noexcept;

        /*
         * Get access to the parsed tokens for applications that want to traverse
         * the pointer.
         */
        std::vector<std::string> const &tokens() const;

        friend bool operator==(json_pointer const &lhs, json_pointer const &rhs) {
            return lhs.tokens_ == rhs.tokens_;
        }

        friend bool operator!=(json_pointer const &lhs, json_pointer const &rhs) {
            return lhs.tokens_ != rhs.tokens_;
        }

    private:
        explicit json_pointer(std::vector<std::string>) noexcept;

        /*
         * Unescape the specified escape sequences, returns false if incorrect
         */
        static bool unescape(std::string &);

        std::vector<std::string> tokens_;
    };
} // namespace melon
